When a semiconductor device, a liquid crystal display device, or the like is to be manufactured by photolithography, a projection exposure apparatus (e.g., a stepper) which transfers, through a projection optical system, the pattern of a reticle as a mask on each shot area on a wafer (or a glass plate or the like) coated with a photoresist is used. In addition to a stepper type projection exposure apparatus, a step and scan type projection exposure apparatus which synchronously scans the reticle and the wafer with respect to the projection optical system to increase the exposure area without increasing the load on the projection optical system is recently becoming popular.
For example, a semiconductor device is formed by overlaying multiple layers of circuit patterns on a wafer. When the circuit patterns of the second and subsequent layers are to be projected and exposed on the wafer, alignment between each shot area on the wafer, on which a circuit pattern has already been formed, and a reticle pattern to be exposed next, i.e., wafer alignment must be accurately performed. As a highly accurate wafer alignment method for the conventional projection apparatus, an alignment method called enhanced global alignment (to be abbreviated as "EGA" hereinafter) disclosed in, e.g., Japanese Patent Laid-Open No. 61-44429 is known, in which the coordinate positions of alignment marks (wafer marks) provided to a predetermined number of selected shot areas (sample shots) on a wafer are measured, and the measurement result is subjected to statistical processing to calculate the array coordinates of each shot area on the wafer.